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1. Humble planar defects in SiGe nanopillars

   https://doi.org/10.1103/PhysRevB.106.054114  

   Yang, Hongbin; Ren, Shang; Singh, Sobhit; Turner, Emily M.; Jones, Kevin S.; Batson, Philip E.; Vanderbilt, David; Garfunkel, Eric (August 2022, Physical Review B)
2. Spin independence of the strongly enhanced effective mass in ultra-clean SiGe/Si/SiGe two-dimensional electron system

   https://doi.org/10.1038/s41598-023-44580-y  

   Melnikov, M. Yu.; Shakirov, A. A.; Shashkin, A. A.; Huang, S. H.; Liu, C. W.; Kravchenko, S. V. (October 2023, Scientific Reports)

   Abstract The effective mass at the Fermi level is measured in the strongly interacting two-dimensional (2D) electron system in ultra-clean SiGe/Si/SiGe quantum wells in the low-temperature limit in tilted magnetic fields. At low electron densities, the effective mass is found to be strongly enhanced and independent of the degree of spin polarization, which indicates that the mass enhancement is not related to the electrons’ spins. The observed effect turns out to be universal for silicon-based 2D electron systems, regardless of random potential, and cannot be explained by existing theories. 

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3. Progress toward a capacitively mediated CNOT between two charge qubits in Si/SiGe

   https://doi.org/10.1038/s41534-020-00314-w  

   MacQuarrie, E. R.; Neyens, Samuel F.; Dodson, J. P.; Corrigan, J.; Thorgrimsson, Brandur; Holman, Nathan; Palma, M.; Edge, L. F.; Friesen, Mark; Coppersmith, S. N.; et al (December 2020, npj Quantum Information)

   null (Ed.)

   Abstract Fast operations, an easily tunable Hamiltonian, and a straightforward two-qubit interaction make charge qubits a useful tool for benchmarking device performance and exploring two-qubit dynamics. Here, we tune a linear chain of four Si/SiGe quantum dots to host two double dot charge qubits. Using the capacitance between the double dots to mediate a strong two-qubit interaction, we simultaneously drive coherent transitions to generate correlations between the qubits. We then sequentially pulse the qubits to drive one qubit conditionally on the state of the other. We find that a conditional π -rotation can be driven in just 74 ps with a modest fidelity demonstrating the possibility of two-qubit operations with a 13.5 GHz clockspeed. 

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4. Thermal resistance across Si–SiGe alloy interface from phonon distribution mismatch

   https://doi.org/10.1063/5.0202880  

   Han, Jinchen; Lee, Sangyeop (April 2024, Applied Physics Letters)

   Interfacial thermal resistance has often been attributed to the mismatch of phonon spectra between two materials and resulting phonon-interface scattering. However, we use the solution of Peierls–Boltzmann transport equation to reveal a substantial nonequilibrium thermal resistance across the interfaces of Si and SiGe alloys at room temperature, despite their nearly identical phonon dispersion and negligible phonon-interface scattering. The Kapitza length of the Si–Si0.99Ge0.01 interface is approximately 600 nm of Si. This originates from the mismatch in phonon distribution between Si and SiGe alloys due to their distinct scattering rates. The mismatch is relaxed by phonon scattering over a region of 1 μm around the interface, corresponding to the upper bound of mean free path Λx of heat-carrying phonons. The relaxation process leads to the significant entropy generation and increased thermal resistance. Introducing a gradual variation in Ge concentration near the interface markedly reduces thermal resistance when implemented over the 1 μm period. Our finding demonstrates that the interfacial thermal resistance can be significant due to the nonequilibrium phonon distribution, even in the absence of phonon-interface scattering. In addition, among various phonon modes with a wide range of Λx, the relaxation of the nonequilibrium is predominantly governed by the phonons with long Λx. 

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5. High-Ge-Content SiGe Alloy Single Crystals Using the Nanomembrane Platform

   https://doi.org/10.1021/acsami.0c02747  

   Bhat, Abhishek; Elleuch, Omar; Cui, Xiaorui; Guan, Yingxin; Scott, Shelley A.; Kuech, Thomas F.; Lagally, Max G. (May 2020, ACS Applied Materials & Interfaces)